Signal lamp



sept. 8,' 1936.

C. H. BRASELTON SIGNAL LAMP Filed Dec. 4, A1951 IN VEN TOR Patented Sept. 8, 1936 UNITED STATES SIGNAL LAMP Chester H, Braselton, New York, N. Y., assgnor to Sirian Lamp Company, Newark, N. J., a corporation of Delaware Application December 4, 1931, Serial No. 578,937

Claims.

This invention relates to lamps, particularly to such lamps as are useful for signalling purposes.

Among the objects of the present invention is 5 to provide an electric signal lamp'which will operate automatically. Another object of the invention is to provide an automatically operating lamp which will function without the use of current interrupting appliances.

A further object is to provide a. signal lamp which is self-contained and incorporates a minimum number of parts. Another object is to provide a signal lamp in which there are no moving parts, either within the lamp itself or in the associated circuit, s o that all that is necessary is that the lamp be applied to the appropriate voltage connections in order to operate.

Further objects will become apparent on consideration of the following specication and accompanying drawing, in which Fig. 1 is a view in elevation of an embodiment of the invention;

Fig. 2 is a detail of the coated lament structure of Fig. 1;

Fig. 3 is a view of a modification of the invention; and

Fig. 4 is a View of another modification.

In Patent No. 2,007,919 dated July 9th, 1933, there is described a type of electric lamp or energy emitter in which a coiloi refractory Wire, such as tungsten, is coated with an electron emitting material and immersed within a container in an atmosphere of inert gases, such as argon or neon. When an electric current is passed from this conductor a halo of luminousgases forms about the diameter and its coatings, which serves, together with the conductor and its coating, as a source of radiant energy which may be in the form of visible light or which may be of radiation primarily in the infra-red or ultra-violet regions.

It is of importance in the manufacture of these lamps that the electron emitting coating be properly applied and treated for use with the lamp. l

In accordance with said application, a filament of appropriate resistance, such, for example, as ohms, is placed in heating relationship with various alkaline oxides, such as the oxides of barium, strontium, calcium or other materials which have been found to emit electrons densely when heated and which have an emissivity in excess of thorium oxide. Thebase filament is tungsten or tantalum wire, although other metal conductors may be used. It is not necessary, ordinarily, that the base material be highly refractory, as the operating temperatures may be relatively low, in many cases not being above that of low red heat.

The filament is preferably coiled and the oxides either applied as a paste to the exterior of the coil, or asa core or rod to the coil interior. The oxide material initially may be in the proportions of 40 grams of barium carbonate, 40 grams of calcium carbonate, 8-grams of barium nitrate with abinder of suicient nitrocellulose 5 dissolved in amyl acetate to hold the coating on the wire. The filament is then mounted on a stem support and sealed in the bulb of the envelope.

The exhaust pump is then connected to the 10 bulb and an oven lowered thereupon to raise the temperature of the bulb and contents to about 400 C., or to as high a temperature as the envelope will stand without softening. Simultaneously, electric current is passed through the 15 lament which is heated to red heat of approximately 600 C. The heat and exhausting process is continued until there is no iiuorescence when the high tension current is directed against the wall of the bulb, or in other words, until 20 there is practically no more gas inside of the bulb. A vacuum of about one-half of a micron is an approximate limiting value.

The current is then increased through the lament so that the temperature thereof is slowly raised until it is about 800 degrees, ora bright red color, the exhaust operation being continued until the newly emitted gases are removed. The oven is then raised from the bulb and the :Elament heated to about 1200n C., the pumping being continued until a high Vacuum oi one-half micron is again obtained.

The pump is then shut 0E and the current turned on, thus completing the process. Where a more complete amalgamation of the coating is desired the following steps are included. About one-half millimeter of neon gas is admitted to the bulb. The filament current is then turned on and gradually increased until a diiused glow completely iills the bulb. When the discharge is uniform throughout the bulb, the iilament current is turned oli and the pump applied to remove the neon gas. The filament temperature is then raised for a short intervai to about 1400 C., with the pump operating to remove any undesirable gases which may have been thrown off during the activation process. Should white discharge spots appear on the filament or support rods, it is an indication that the gases or vapors within the bulb have not been completely re- 50 moved, and the bulb is again exhausted and the Whole process of activation repeated.

With the actuation process satisfactorily completed, the filament circuit is disconnected and the pump turned oi and the appropriate amount of gas admitted to the bulb. In one form of my invention I utilize neon and argon gases in the relative amounts of 50 mm. of neon gas, and 150 mm. 'of argon. Other monatomic gases, such as krypton, and helium, or metal vapors such as 6 those oi' mercury, caesium and rubidium may also be used. The bulb is then sealed of! and a small quantity of magnesium flashed to absorb additional impurities, thus completingl the process.

Applying the principles involved in the preparation and application of the coating hereinabove described, I employ a lamp bulb Il, which may be of transparent material, as of glass, in which is sealed a support II, containing standards I2 and I3, to the outer ends of which are attached lead-in wires I4 and I5, adapted to be connected to a source of electric potential. Intermediate the standards I2 and I3 within the bulb is the tungsten coil I6 on which the coating I1 of electron emitting material, as hereinabove described, is applied. The dimensions of the coil with the applied coating are such as to be suitable for the particular voltage for. which the lamp is intended. For instance, where the lamp-is to be used for a commercial voltage of volts, a greater length of filament is necessary than for lower voltages. The turns of the coil II, as illustrated in Fig. 2, are relatively close together so as to insert a maximum amount of resistance. The ends of the coil are welded or otherwise attached to the nickel supports I2 and I3, which in turn are spaced apart so that the coil I6 may be suspended in approximately horizontal position. Where the length of the coil is excessive it may be necessary to add a third standard which may be positioned intermediate the standards I2 and I3 and contact at approximately the midpoint of the coil.

Within the container or envelope I0 is an atmosphere of inert gases, such as those hereinabove mentioned. These gases should be chenilcally pure, or at least have impurities not exceeding one percent by volume. I have found argon and neon to be particularly desirable, the proportionlor amounts being approximately 50 mm. of neon and mm. of argon, totaling about 200 mm. of gas. Other pressures may be used, as I have found that pressures below 50 mm. and in excess of 350 mm. are possible and give satisfactory results.

The operation of the lamp as hereinabove described for signalling purposes is as follows. When an electric potential is applied to the leadin wires I4 and I5, the coil I6 becomes heated, causing the coating Il to emit electrons in profusion, thereby ionizing the adjacent gases which form a sheath or layer of highly activated gases adjacent the coating. Should, however, the voltage applied to the conductor I6 be diminished, a, point would be reached at which there is a critical balance between the gas pressure and the temperature of the coating, as well as with the drop of potential of the electric circuit along the coil IB. At this critical state the sheath or halo of gases about the conductor alternately collapses and develops with a certain definite frequency, which frequency may be made to vary by a slight change in the voltage, which in this way modifies the heat conditions and the potential drop. In one form of lamp I have found a pressure of about 200 mm. of mercury for the gas necessary to obtain the variable eil'ects when a voltage oi' thirty-three volts was applied to the conductor. The basis of the iluctuation appears to lie in the fact that at the critical point the potential along the lament axis is identical to the breakdown potential of the heated and ionized gas adjacent the illament for the gas pressure prior to the formation of the halo. As soon as. the halo forms, however, with its sudden increase in the heat content of the gas the increased pressure immediately increases the ionization constant and the halo disappears.

'Ihis alternate making and breaking of the luminous or ionized gas layer is useful where a signalling operation is desired. For visible signailing the container III should be transparent and the sheath or gas layer luminous. By modifying the gases it is possible to vary the color of the luminescence so that color, combined with the ickering of the light radiation, serves to call attention to the signal. Such a device would be useful as a signal for street intersections, or it could be used as a means for drawing attention to any other point. Such a device might be used also as asource of intermittent invisible radiation for various purposes.

In Fig. 3 of the drawing I have indicated a modification of the invention showing a modified arrangement of the lamp elements. Within the bulb or envelope 20 there is the usual support 2| on which is mounted the two standards 22 and 23, which in turn are attached to the lead-in wires 24 and 25. The lstandard 22 is extended in a straight section 26, which is coated with electrically insulating material, such as glass tubing 21, to prevent short-circuiting. To the upper end of the standard 26 is mounted a cross bar 28, and between the end of this bar and the standard 23 is attached the filament of the lamp. The illament takes the form of three coiled sec- -tions 29, 30, and 3I, each separated by a length of conducting wire 3l and 35, the wire 3| having connection by means of the wire 36 to a glass bead 31, formed on the tubing 2l, and the rod 35 having connection by means of the wire 38 to a glass bead 39 formed on the glass rod 21.

Appropriate inert gas, such as that hereinabove described, is included within the envelope immersing the various elements. Also, a coating 40 of electron emitting material is placed on the various sections29,30,and3l of the lament. 'Ihe operation of this lamp is similar to that shown in Fig. l, with the exception that higher voltages are available in a lamp of this type than are possible in a lamp built according to Fig. 1.

In the modification of Fig. 1, for instance, an appropriate working potential has been ascertained as intermediate 20 and 40 volts. Where 110 volts or more are employed it may be expedient to divide the lament into sections of three or more, as shown in Fig. 3, to each of which a voltage less than 40 volts could be applied. Alternatively, a group of low potential lamps may be connected in series where use is made of 110 volts.

In the various modiiications, electron emitting material is described as in the shape of a coating applied to the conductor. I have found, however, that this material may be mixed with the conducting substance, and by this means, electron emission increased over that possible from a plain conducting substance. For example, I may mix the electron emitting material with the conductor in powdered form, and the mixture treated so as to form a conducting iilament; or I may chemically combine the conductor and the oxide to form a filament, such as thoriated tungsten, which is the result of a combination of tungstic acid and thorium nitrate. The coated material may be applied as a rod forming the core of the coil. The rod may have various shapes, one shape which I have found useful being triangular in section so that there are not over three points of contact with the insoupes terior of the coil. In this manner the ionization is limited.

In Fig. 4 I have illustrated a modification of the invention in which means is provided for varying the pressure of the gas within the container. For this purpose the container is provided with a tubular outlet SII having an annular bead 5I formed thereupon. To the tube Il there is connected a pressure modifying unit 52 which consists of a cup-shaped base 53 having a central outlet 54 provided with an outwardly turned l flange 55 adapted to seat in the annularl bead 5| o! the glass outlet 5B. The base 53 and central connection 54 are of metal. the connection being of iron-nickel coated with copper, or of other metals which have, either singly or in combination, a co-eillcient of heat expansion simllar to that of glass and which will permit an air-tight welded Joint with glass. Alternatively, cement may be used intermediate the glass neck and the cup base out1et,such as that of silver solder. A

The base 53 is faced by a diaphragm plate It of exible metal corrugated annularly and having a central ilat portion 51 forming the contact area for the end of the screw 58 threaded in the cover plate 58. The plate 59 has an edge Il with an inwardly turned flange il engaging the under portion of the base 53 and retained thereby. 'I'he screw 58 is provided with a head I2 by means of which the position of the diaphragm 51 is varied, and thereby the capacity of the diaphragm unit is varied. In order to adjust the diaphragm independently of the pressure in the container, the end of the screw is provided with' a circular groove 6I in which a projection 0I fastened to the diaphragm contact area l1 is in constant engagement. It is apparentr that the diaphragm follows the movement of the screw whether it is moved inwardly or outwardly, and in this manner the capacity of the container is varied.

Instead of the diaphragm unit as shown other equivalent means may be utilized i'or modifying the capacity of the container, such, for example, as trapped mercury in a tubular container having a ilexible connection to the container outlet 50. Modification of the pressure in the container may also be obtained'by utilizing a glass tubular connection terminating in an enlarged bulb which may be heated by a gas name, for example.

Attention le directed to the met that while the coated conductor may be coiled, as shown in Fig. 2, it is within the scope of the invention to employ a straight, uncoiled, coated conductor. Also, it has been found ldesirable to enlarge the current carrying capacity of the conductor at the section intermediatethe coating and the point of adjustment to the standards I2 and I3. This may be done by increasing the diameter of the wire at this point or by various other means, such as to insert a short secondary coil over the coated end of the conductor and weld the other end to the support, thus giving two current carrying paths for the current from the main portion of the current conductor. This construction obviates fracture due to increase in current arising from flow through the ionized gases. 'I'he increase in the diameter of the conductor end should not be too 'great as to cause cooling of these ends. inasmuch leakage, insulate the standards I2 and I3 by in- Same.

serting thereon-a tube of glass or other highly resistant material, or by coating the same with substances nonconductive to,electricity, such, for example, as described in my Patent No. 2,039,772, dated May 5, 1936. l

Various other modifications of the invention 'will be apparent to those skilled inthe art. to

that `of thorium oxide between lead-in wires sealedin a part of a closed container containing an inert ionizable gas, the breakdown potential of said gas per unit length when heated in the region adjacent the conductor being within the' normal operative voltage range of a unit length of th'e conductor and the amount oi' said current being increased gradually from zero to a point where the breakdown'gas potential per unit length and the potential per unit length along the conductor are equal.

2. A process of bringing about a iluctuating energy emission from a radiating source consisting of an electric conductor coated with electron emitting material having an emissivity in excess of that of thorium oxide which consists in enclosin g said source in an envelope containing an inert ionizable gas at a given pressure; and raising the potential oi the conductor per unit length to a point where it is equal to the breakdown potential of theheated gas adjacent the conductor.

3. In a lamp adapted to produce a fluctuating `200 mm. of mercury.

4. A process of producing ailuctuating radiation from an energy source which consists in mounting a conductor coated with electron emitting materials having an emissivity in excess o! that of thorium oxide between lead-in wires sealed in a part of a closed container containing an inert ionizable gas, passing an electric current through said conductor; and varying the potential of the current and gas pressure till a value of potential and ci pressure is obtained at which the breakdown potential of the gas and potential along the conductor per unit length are substantially the same.

5. The process of producing a fluctuating emission from an energy source which consists in mounting an electric conductor containing alkaline earth metal oxides adapted to emit electrons when heated between lead-in wires sealed in a glass containericontaining an ionizable gas; passing an electric current through said conductor; and gradually increasing the potential of' the current from zero up to a point where the breakdown potential of the gas and potential along the conductor per unit length are substantiallythe CHESTER H. BRASELTON. 

